It is known to make windshields by laminating a first ply of glass, a plastic interlayer, and a second ply of glass. Before 1960, the plies of glass used in this process were ground and polished plate glass, which has excellent freedom from distortion. More recently, it has been customary to use float glass from 1.1 to 4 mm thick for the first and second plies. The float glass is produced by a process such as that described in U.S. Pat. Nos. 3,083,551 and 3,700,542.
In a float glass process, glass is drawn in a direction. This process tends to cause optical distortions in the glass, also known as draw lines. These draw lines are optical distortions that extend parallel to the direction that the glass is being floated. Typically, the draw lines include a series of semicylindrical lenses at each surface of the drawn glass relative to a center plane of the glass. The draw lines are substantially parallel to one another and alternate between convex and concave approximate semi-cylindrical lenses.
When forming windshields, it is desirable to minimize the distortions and improve optical quality. To do so, it is conventional wisdom to align the draw lines of the first ply with the draw lines of the second ply to minimize distortion. To cross the draw lines or to arrange them perpendicularly to one another is known in the art to cause severe optical distortions thereby rendering the windshield unusable. Accordingly, there remains opportunity for improvement.